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Dear Shi Kong,<br>
<br>
We have very few data to answer properly to your question. What are the
available experimental data and more specifically:<br>
1/ Do you have the atomic structure (cell param. and atomic positions)
for different pressures or only cell parameters variation with pressure?<br>
2/ In the "normal" structure how many equivalent sites do you have for
the f-element? 1 or more?<br>
<br>
If you have one equivalent position for the f-element in the "normal"
structure, then in the supercell you have many inequivalent sites for
the f-element.<br>
In other words, during the calculation of the small cell you can easily
converged to metal state because all f-atoms are equivalently occupied.
In contrast, in the supercell you allow to have different electronic
configurations for the f-atoms in inequivalent sites. In such
situation, you should be very careful during the SCF convergency,
because you could have charge oscillations due to the alternative
occupation of the inequivalent f-atoms. In addition, you should need to
help the system to converge towards the "global" minimum electronic
configuration using such an approach:<br>
- change the smearing method (efmod in case.in2), i.e. use GAUSS for
instance with large eval value at the beginning to 0.05<br>
- reduce progressively eval <br>
<br>
But it should also be due to an incorrect model for the high pressure
structure:<br>
- because you do not have enough or accurate experimental data <br>
- because the supercell you have generated exhibits an ordering which
lead to the opening of a band gap. <br>
<br>
Regards<br>
<br>
Xavier<br>
<br>
<br>
kongshi a ¨¦crit :
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<div><font face="Calibri">Dear WIEN2k users:</font></div>
<div><font face="Calibri"> Recently I'm calculating the
f-electron material under pressure with LDA+U. There are different
results between with normal structure file and with supercell structure
file. The result of normal structure file with symmetry under pressure
is metal. But the supercell structure under pressure result is
insulator. The result of spuercell structure file in atmospheric
pressure is metal. In my opinion the pressure drive the material to the
metal state.</font></div>
<div><font face="Calibri"> Can anybody tell me what the
problem is? Thank you in advance.</font></div>
<div> </div>
<div> </div>
<div><font face="Calibri">shi kong</font></div>
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<br>
<br>
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